750 THE GEOLOGY OF MINNESOTA. 



[Agglomerate . 



Meg. Fine grained, light green. 



Mir. There is a very fine, almost structureless mingling of all the products of 

 change of basic rock materials, viz., calcite, leucoxene, chlorite, glassy feldspar, sericite. 

 There are, besides, areas over which the general extinction is simultaneous, though 

 enclosing numerous of the above minerals, due apparently to the remnant of old 

 feldspar crystals whose characters are otherwise undiscoverable. 



There is a general elongation of all the substances in one direction, making a 

 close schistosity. One section. 



Age. Archean (Keewatin). N. H. \\. 



No. 1624. AGGLOMERATE. 



From the greenstone agglomerate cut by the railroad at Ely. Same rock as No. Ifil I. 

 Ref. Annual Report, xx, page .'54 ; American Geologist, vol. ix, page 3.V.). 



Mr;). Fine grained, with amygdaloidal tubes of calcite. Part of the scale that 

 surrounds the bombs. 



Mir. The section shows only the rock, which is in all respects the same as No. 

 1511, and especially in showing in part a somewhat radiated or sheaf-like arrange- 

 ment of the little feldspars. One section. 



Aye. Archean (Keewatin). N. H. w. 



No. 1625. AGGLOMERATE. (Basic.) 



Same place as No. 1624. 



Ref. Annual Report, xx, page 34. 



Met/. Some of the dark green schistose rock that fills the interspaces- between 

 the bombs. 



Mic. Chlorite, calcite, leucoxene, and scattered small grains of a highly polarizing 

 mineral which is certainly secondary, resembling epidote; these compose the rock, 

 but the latter two are in the form of isolated small grains in the large masses of the 

 former two. There is also a little pyrite. One section. 



Aye. Archean (Keewatin). 



Remark. The internal structure of No. 1624 is plainly igneous; that of No. 

 1625 has no suggestion of igneous origin. N. H. w. 



No. 1626. AGGLOMERATE. 



Same place as No. 1024. 



Ref. Annual Report, xx, page 34 ; Annual Report, xxiii, pages 204, 213. 



Meg. A part of the bomb from toward the centre. Compare No. 1511. 



Mic. The feldspars are fine, and are arranged in radiated or sheaf-like clusters. 

 They are long and slender. Much leucoxene clouds the rock. There are a few 

 isotropic areas of chlorite and many scattered grains of calcite. One section. 



Aije. Archean (Keewatin). 



